Proton Transport from the Antimatter Factory of CERN

The antiproton is a basic constituent of antimatter and required for stringent matter-antimatter comparisons to test the fundamental charge-parity-time (CPT) reversal invariance in the Standard Model of particle physics (1). Using low energy antiprotons, only available at the antimatter factory (AMF) located at CERN (2), such tests have been realized for example in the high-precision spectroscopy of antiprotonic atoms (3), and antihydrogen (4). In our cryogenic Penning-trap experiments (5), we measure the fundamental properties of protons and antiprotons and conduct CPT tests comparing their magnetic moments with a precision of 1.5 parts per billion (6, 7), as well as the most precise test of CPT invariance in the baryon sector by comparing their charge-to-mass ratios to a relative uncertainty of 16 parts-per-trillion(8). Although innovative shielding systems have been implemented (9), our experiments are limited by magnetic field fluctuations imposed by the accelerators in the AMF. To push the limits of our measurements, we are advancing the relocation of antiprotons to dedicated precision laboratories. This work presents a critical milestone in this endeavor: the successful transport of a trapped proton cloud from the AMF using BASE-STEP (10) — a transportable, superconducting, persistent, autonomous, and open Penning-trap system. We transferred the trapped protons from our experimental area at the AMF onto a truck and transported them across CERN’s Meyrin site. We demonstrated loss-free proton relocation, sustaining autonomous operation without external power for four hours, thereby confirming the feasibility of transferring particles to low-noise laboratory environments. The transport range of this system can be extended using mobile power generators (11) to reach laboratories throughout Europe. Our achievement represents a breakthrough and a potential start of a new era in precision antimatter research by conducting antiproton spectroscopy in low-noise laboratories. It also enables transportation and offline studies of other exotic ions, such as highly-charged ions produced in accelerators (12) or high-end EBITs (13), and the charged antimatter ions H¯ + (14) and H¯2 (15)